Best Battery for MerCruiser 888 (1976 Ford 302)

[ratdude747]

Question: My 1976 Starcraft Montego (Mercruiser 888, carbed 302) had a group 65 Car Battery in it. I pulled that battery to put in my truck, as it's obviously the wrong battery, like a lot of auto parts on the boat that didn't belong and have since swapped out. I'd like to know what suggestions are out there for a proper battery to put back in.

It has been previously converted to a PMGR-type starter (and unlike the rest of it, they actually used a marine rated starter!), so the cranking amp requirement is likely a lot less (based on past experience PMGR swapping one of my Ford trucks). The other electrical mods are a Pertronix Ignitor electronic ignition (points and ballast wire removal + new coil), 4 barrel carb swap (holley with choke heater, likely similar and rewiring the starting circuit with a fresh relay (as the previous setup wasn't quite right, direct driving the solenoid with the igntion switch ). There also is some aftermarket fan/heater thingy mounted under the console, but it currently isn't wired. Otherwise, everything is stock or stock-equivalent in terms of wiring (no added stereo/GPS/etc.).

 

[Bondo]

Ayuh,..... This is in my barge, 'n will work for you,.....

 

[ratdude747]

Ayuh,..... This is in my barge, 'n will work for you,.....

Sounds good. And the dimensions should make clearing the fuel hoses slightly easier (skinnier and taller, the wide group 65 took some gymnastics to remove/install).

Edit: for $55 less I can get one of these. Same size, but also marine deep cycle rated and has higher CA rating (Maybe, 705 CA vs 750 MCA). Last I checked Clarios (ex-Johnson Controls) still makes Everstart batteries and I've generally had good luck with them.

That an acceptable substitute?

 

[Lou C]

I have something similar (a pair of gp 27 Deka marine dual purpose batteries) & a 1,2,1+2 & off switch. This set up has worked well over the years for me…

 

[Bondo]

Sounds good. And the dimensions should make clearing the fuel hoses slightly easier (skinnier and taller, the wide group 65 took some gymnastics to remove/install).

Edit: for $55 less I can get one of these. Same size, but also marine deep cycle rated and has higher CA rating (Maybe, 705 CA vs 750 MCA). Last I checked Clarios (ex-Johnson Controls) still makes Everstart batteries and I've generally had good luck with them.

That an acceptable substitute?

Ayuh,..... Sure,.... plastic boat battery boxes are usually group 24, or group 27,.....

 

[ratdude747]

Ayuh,..... Sure,.... plastic boat battery boxes are usually group 24, or group 27,.....

I don't have a battery box... just a nylon strap with a pair of plastic cleats.

 

[Bondo]

I don't have a battery box... just a nylon strap with a pair of plastic cleats.

Ayuh,..... The idea of a battery box is to securely cover the battery, so a dropped piece of metal, can't short out the terminals, causing a spark, 'n resulting explosion,....

 

[Lou C]

I used to use boxes but ditched them because:
1) the batteries never fit tight in them & move around
2) that strap always gets loose & the whole thing moves
I have gone to battery hold downs & have the rubber insulators on the pos & neg clamps. Much better!

 

[Scott06]

Sounds good. And the dimensions should make clearing the fuel hoses slightly easier (skinnier and taller, the wide group 65 took some gymnastics to remove/install).

Edit: for $55 less I can get one of these. Same size, but also marine deep cycle rated and has higher CA rating (Maybe, 705 CA vs 750 MCA). Last I checked Clarios (ex-Johnson Controls) still makes Everstart batteries and I've generally had good luck with them.

That an acceptable substitute?

Maybe an acceptable substitute. May just be luck but the batteries have gotten at NAPA seem to hold up well n terms of longevity. The cheaper ones have bought at Walmart or other cheaper auto parts stores, not so much.

While a few bucks more might be a better investment

 

[ratdude747]

Maybe an acceptable substitute. May just be luck but the batteries have gotten at NAPA seem to hold up well n terms of longevity. The cheaper ones have bought at Walmart or other cheaper auto parts stores, not so much.

While a few bucks more might be a better investment

Also availability. The local Napa doesn't have them (but all the ones one county over do, go figure) but the local Walmart does. Yes, Napa will do a ship to store (or I could drive out to one of the other ones), but honestly, I don't see the point of going through extra hassle just to pay 77% more ($168 vs $95, Walmart has no Core charge and I'm planning not to turn in a core) I'll take a look at Walmart after work... if somebody other than Clarios is making it, I may do something else. Napa has Clarios or East Penn making theirs so either the same thing (with a different sticker) or something likely on par (never used East Penn-made batteries). At least it's not a modern Exide (whose batteries I've heard/seen are junk these days).

---

It's a real bear getting the old battery in and out of the boat. I had to slide it along the side of the engine bay, then turn it at a weird angle to get it past the fuel tank fill/vent hoses and the alternator. Vertically the aformentioned hoses block lifting it vertically. Which is why I'm hesitant to add a box, as such may result in an uninstallable condition (without disconnecting hoses from the fuel tank, no thanks). I have a similar strap in one of my trucks (the one I moved the old battery to) and it's always held tight (even when I KO'd a deer in it and had to rebuild the front bodywork!).

 

[Lou C]

Amazon.com

this but be sure to get rubber insulators to cover the positive and negative battery terminals to prevent short circuits.

 

[ratdude747]

Amazon.com

this but be sure to get rubber insulators to cover the positive and negative battery terminals to prevent short circuits.

Will do on the rubber. Probably should for the starter relay I installed as well:

 

[Lou C]

 

[ratdude747]

Made it to Walmart. Found a very fresh one:



Based on the serial number, I'm pretty sure this is a Clarios made unit:



(JC meaning Johnson Controls?)

Winner?

 

[ROY WILLIAMS]

my 1977 Mercrusier manual the MCM888 ... did the wiring of that schematic.... in the BOAT forums ratdude .....


also my the 1977 engines manual Mercrusier ...... all engines .....
my MCM470 ....

 

[ratdude747]

my 1977 Mercrusier manual the MCM888 ... did the wiring of that schematic.... in the BOAT forums ratdude .....


also my the 1977 engines manual Mercrusier ...... all engines .....
my MCM470 ....

Not sure what you're trying to say here.

The boat came with the schematics as part of the Mercruiser installation manuals stuffed in the glove box (which I've since scanned in).

AFAIK battery size/capacity was never listed.

A long side note about the relay added and what's going on there:

The starter relay was the second part of a PMGR stater upgrade (it's a Ford thing). The first part was already done... but not done right.

When converting a "1 wire" (Moving pole shoe, etc.) stater to a PMGR (or other starter with a separate solenoid), the usual wiring conversion goes like this:



(borrowed from another of the forums I'm a member of)

What the PO had done was move the main starter power as one is supposed to, but instead of using the now empty side of the stater relay as the solenoid control, they chopped the relay control wire mid-harness and wire nutted a loose wire from the solenoid direct to the now-cut ignition switch wire in the harness. This likely contributed to the ignition issues that marooned the boat in the first place (no ballast bypass during crank). My conversion to a Pertronix ignition (no more ballast wire, powered directly from RUN) should mitigate that aspect though; the Pertronix Igniter can operate just fine at cranking voltages and Starcraft happened to use an ignition switch that has RUN hot during START.

I don't know why the PO did that... PMGR solenoids draw around 42A, well above what an ignition switch designed for a relay drive is likely good for. They also tossed the nuts off the existing starter relay (at this point just a power distribution stud)... and with said relay (and the other half of the cut harness wire) also a pain to access and its condition unknown, I decided the best option was to obtain a marine rated starter relay and mount it somewhere easier to access that also worked with the "new" wiring.

The new relay is a marine-rated Mallory unit (NOS eBay, for a Mercruiser starter solenoid application). It gets power and ground from one of the trim relays; I also added a flyback (snubber) diode (the red/black taped thingy) since the relay doesn't have any protection (this is to ensure the relay coil doesn't become an ignition coil and arc up the ignition switch). I haven't tested it yet, but it was working a few months ago with a temporary Bosch-style "ice cube" relay in place of the new relay.

This boat wasn't quite "stock" when I got it, and for "hidden" things, I see no point in keeping stock if the easier/better non-stock option is safe, affordable, and reliable.

 

[ROY WILLIAMS]

Not sure what you're trying to say here.

The boat came with the schematics as part of the Mercruiser installation manuals stuffed in the glove box (which I've since scanned in).

AFAIK battery size/capacity was never listed.

A long side note about the relay added and what's going on there:

The starter relay was the second part of a PMGR stater upgrade (it's a Ford thing). The first part was already done... but not done right.

When converting a "1 wire" (Moving pole shoe, etc.) stater to a PMGR (or other starter with a separate solenoid), the usual wiring conversion goes like this:

View attachment 395150

(borrowed from another of the forums I'm a member of)

What the PO had done was move the main starter power as one is supposed to, but instead of using the now empty side of the stater relay as the solenoid control, they chopped the relay control wire mid-harness and wire nutted a loose wire from the solenoid direct to the now-cut ignition switch wire in the harness. This likely contributed to the ignition issues that marooned the boat in the first place (no ballast bypass during crank). My conversion to a Pertronix ignition (no more ballast wire, powered directly from RUN) should mitigate that aspect though; the Pertronix Igniter can operate just fine at cranking voltages and Starcraft happened to use an ignition switch that has RUN hot during START.

I don't know why the PO did that... PMGR solenoids draw around 42A, well above what an ignition switch designed for a relay drive is likely good for. They also tossed the nuts off the existing starter relay (at this point just a power distribution stud)... and with said relay (and the other half of the cut harness wire) also a pain to access and its condition unknown, I decided the best option was to obtain a marine rated starter relay and mount it somewhere easier to access that also worked with the "new" wiring.

The new relay is a marine-rated Mallory unit (NOS eBay, for a Mercruiser starter solenoid application). It gets power and ground from one of the trim relays; I also added a flyback (snubber) diode (the red/black taped thingy) since the relay doesn't have any protection (this is to ensure the relay coil doesn't become an ignition coil and arc up the ignition switch). I haven't tested it yet, but it was working a few months ago with a temporary Bosch-style "ice cube" relay in place of the new relay.

This boat wasn't quite "stock" when I got it, and for "hidden" things, I see no point in keeping stock if the easier/better non-stock option is safe, affordable, and reliable.

the internet https://www.marineengine.com/newparts/part_details.php?pnum=ARC50169

my MCM470 1978 did the engine starter ......
inspected it and the brushes / armature /and the grease bearings ....
my electrical/mechanic/electronic 50 yrs .... I was the electrical trains subway ... BOSTON ,MA ....US NAVY .....WAR VETERAN

 

[ratdude747]

the internet https://www.marineengine.com/newparts/part_details.php?pnum=ARC50169

my MCM470 1978 did the engine starter ......
inspected it and the brushes / armature /and the grease bearings ....
my electrical/mechanic/electronic 50 yrs .... I was the electrical trains subway ... BOSTON ,MA ....US NAVY .....WAR VETERAN

The current starter is the newer design (Ford PMGR) that were used on later Mercruiser 302's. Here's a pic of it from last year:



Unless one is doing a Concours restoration (which I absolutely am not), the old 1 wire starters are not worth keeping in my opinion. They draw a lot more current and (at least with Ford's moving pole shoe units) chew the ring gears (due to the pinion spinning while advancing, rather than advancing and only spinning once advanced). The newer Chrysler-style PMGR is a much improved design; the dedicated solenoid fixes the chewed teeth issue, and the gear reduction motor is a lot more efficient (read: faster cranking, easier starting, and less battery load/draw during starting). The only reason Ford used the moving pole shoe design in the first place was to save the cost of a solenoid...

Either way, I'm not swapping starters since what I have works, is marine rated, and what my current wiring is setup for. Again, this isn't a Concours restoration, so "under the deck" upgrades aren't an issue!

 

[Scott06]

The current starter is the newer design (Ford PMGR) that were used on later Mercruiser 302's. Here's a pic of it from last year:

View attachment 395153

Unless one is doing a Concours restoration (which I absolutely am not), the old 1 wire starters are not worth keeping in my opinion. They draw a lot more current and (at least with Ford's moving pole shoe units) chew the ring gears. The newer Chrysler-style PMGR is a much improved design; the dedicated solenoid fixes the chewed teeth issue, and the gear reduction motor is a lot more efficient (read: faster cranking, easier starting, and less battery load/draw during starting).

Yes most folks are converting to PMGR for weight savings and easier install. Only issue I have heard is sometimes the PMGR is slightly shorter than the original and you need to get new bolts, which is not a bad idea anyways

 

[ROY WILLIAMS]

The current starter is the newer design (Ford PMGR) that were used on later Mercruiser 302's. Here's a pic of it from last year:

View attachment 395153

Unless one is doing a Concours restoration (which I absolutely am not), the old 1 wire starters are not worth keeping in my opinion. They draw a lot more current and (at least with Ford's moving pole shoe units) chew the ring gears. The newer Chrysler-style PMGR is a much improved design; the dedicated solenoid fixes the chewed teeth issue, and the gear reduction motor is a lot more efficient (read: faster cranking, easier starting, and less battery load/draw during starting).

so my MCM470 is that Mercrusier starter is a great !!!!! no corrosion !
so my cars are did the solenoid and the motor starter is a mess of that corrosion .... PMGR